This is one of the major differences between flatMap () and map (), where map () transformation always returns the same number of elements as in input.
What is the difference between flatMap () and map () in Apache Spark? Technically because Unit doesn’t implement GenTraverableOnce. So flatMap will runs map on every element of sequence, and then run flatten. Why can’t we use flatMap in unit tests in Scala?īecause flatMap is a combination of map and flatten. Stream flatMap(Function mapper) is an intermediate operation. Stream flatMap(Function mapper) returns a stream consisting of the results of replacing each element of this stream with the contents of a mapped stream produced by applying the provided mapping function to each element. So what’s the exact difference between map and flatMap: map transforms items emitted by an Observable by applying a function to each item whereas flatmap: Applies a specified function to each emitted item and this function in turn returns an Observable for each item. What is the difference between map and flatMap in Javascript? In this sense, it works like the opposite of filter. In other words, it allows you to map many items to many items (by handling each input item separately), rather than always one-to-one. Can I use flatMap?įlatMap can be used as a way to add and remove items (modify the number of items) during a map. There are two kinds of Maps, the immutable and the mutable. Keys are unique in the Map, but values need not be unique. Any value can be retrieved based on its key. Scala map is a collection of key/value pairs. flatMap : Similar to map, it returns a new RDD by applying a function to each element of the RDD, but output is flattened. What is the difference between map and flatMap in spark?Īs per the definition, difference between map and flatMap is: map : It returns a new RDD by applying given function to each element of the RDD. It is similar to Map, but FlatMap allows returning 0, 1 or more elements from map function. It applies to each element of RDD and it returns the result as new RDD. What does flatMap in Spark do?Ī flatMap is a transformation operation. In the FlatMap operation, a developer can define his own custom business logic.
But flatMap (loosely speaking) transforms an RDD of length N into a collection of N collections, then flattens these into a single RDD of results.Ī flatMap is a transformation operation. Now, map transforms an RDD of length N into another RDD of length N. What is the difference between map and flatMap and a good use case for each? The difference is that the map operation produces one output value for each input value, whereas the flatMap operation produces an arbitrary number (zero or more) values for each input value. What is the difference between map and flatMap stream operation?īoth map and flatMap can be applied to a Stream and they both return a Stream.
The flatMap() is used to produce multiple output elements for each input element.įlatMap() method is method of TraversableLike trait, it takes a predicate, applies it to each element of the collection and returns a new collection of elements returned by the predicate. The map() transformation takes in a function and applies it to each element in the RDD and the result of the function is a new value of each element in the resulting RDD.
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